Free-piston generator of electric current



Sept. 24, 1963 R. JAMES, JR

FREE-PISTON GENERATOR OF ELECTRIC CURRENT 1 i EMAggETS i Filed Aug. 5,1960 WEIGHT CERAMIC INSERTS LAMINATED METAL INVENTOR.

RALPH JAMES, JR.,

BY MJL 27M ATTORNE Y.

United States Patent 3,105,153 FREE-HSTON GENERATGR (3F nrnornro CURRENTRalph James, Jr., Channelview, Tex, assignor, by mesne assignments, toEsso Research and Engineering Company, Elizabeth, N.J., a corporation ofDelaware Filed Aug. 5, 1960, Ser. No. 47,686 3 Claims. (Cl. 290--l) Thisinvention relates to generators of electric current and particularly toa free-piston reciprocating engine in which current is generateddirectly by the reciprocation of a freely moving piston actuated by theexpansion of a fluid.

Because of its high thermal eificiency, a number of free-piston powergeneration stations have been constructed. Some of these powergeneration stations include therein a reciprocating member havingappropriate means for generating an electric current. However, all ofthe previous reciprocating free-piston type power generating deviceshave been bulky and/or have included a plurality of moving parts. Formany applications requiring the generation of electric power, it ishighly desirable that the power unit be as small and compact aspossible. One example of such an application is the power for a unit airconditioner. Many other applications requiring small and compact unitswith a minimum number of moving parts can be mentioned.

The invention to be described herein provides the art with a small,compact reciprocating free-piston type electric power generator whichhas only one moving part, the reciprocating piston. Piston shafts,piston synchronizing linkages, slip rings, and various other elementswhich are necessary in currently utilized electric current generatingunits are eliminated by this invention. This invention is simple andcompact, hence, can be made at relatively low cost. The structure isalso such that a complete overhaul of the generator can be made simply,quickly, and cheaply.

The invention as well as its many advantages will be further understoodby reference to the following detailed description and drawing in which:

FIG. 1 is a schematic sectional elevational view showing a preferredembodiment of the invention, and

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1.

Referring to the drawing, the new generator of electric current includesa cylinder 10 having a combustion chamber 12. A free-piston 14 isdisposed within the chamber 12 for reciprocating motion withinthe'cham-ber 12. Upper and lower piston rings 16 are mounted about theouter periphery of the solid piston 14. A portion of the piston 14 isprovided with permanent magnetic material. To this end, the permanentmagnets 24 and 26 are provided within the piston 14 and extendingtransversely across said piston.

An upper air-fuel mixture inlet 28 and an upper exmixture inlet 32 and alower exhaust 34 are provided within the cylinder all}. The air-fuelmixture is fed into the chamber 12 through inlet 28. Upon upwardmovement of the piston 14, the mixture is compressed and exploded tomove the piston 14 downwardly. The exploded gases are exhausted throughexhaust 30. As the piston 14 moves downwardly, it compresses theair-fuel mixture which has previously been fed into the lower portion ofthe chamber 12 through inlet 32. These gases are compressed and explodedto move the piston upwardly again with exhaust gases going out of theexhaust 34. The cycle is continuously repeated. Valves are provided ininlets 28 and 32 and outlets 3t and 34 to provide proper timing for thefeeding of the air-fuel mixture to the chamber at the proper time. Thesevalves (not shown) are conventional and well known to those skilled inthe art.

Annular recesses 36 are formed within the inside wall of the cylinder 10and extend outwardly from the chamber 12. Recesses 36 extend into thelaminated metal 38. The lamina-ted metal portions are held together bybolts 40 and nuts 44. The laminations provide for temperature control,and provide high permeability magnetic flux paths.

Mounted within each of the recesses 36 are insulated coil windings 48.These windings can be arranged in series. Grooves or holes 39 may beformed through the lam-inations 3-8 to receive wires for connecting thecoil windings 48 in series.

An annular insulating insert 50 is inserted in the entrance of eachrecess 36. The inserts Sit are made of a high heat resistant materialsuch as ceramic, quartz, or epoxy. The inserts Stl are primarily toprovide smooth inner walls to avoid piston ring snagging. The insertsalso serve to protect the coils against products of combustion, oil,etc., as well as provide some insulation from heat. The alternatingcurrent output is conducted from the reciprocating electric currentgenerator by means of conducting lines 52 and 54.

The lower extremity of the cylinder 10 is provided with a cylinder head56. The cylinder head 56 is detachably secured to the cylinder '10 bymeans of bolts 53.

An upper pressure transducer 62 and a lower pressure transducer 64 areprovided in the upper portion of the cylinder 10* and the cylinder head56, respectively. Ports as and 68 provide for passage of pressure fromthe upper part of chamber 12 and the lower part of chamber 12 to thepressure transducers 62 and 64, respectively. As the pressure within thechamber 12 increases due to the approach of the piston =14 toward aparticular pressure transducer, a particular pressure is reached andsensed by the transducer to generate an electric signal to trigger aspark plug 70, located in the upper portion of the cylinder 10, or 72,located in the lower portion of cylinder 10.

in operation, the alternate injection of the air-fuel mixture intoinlets 28 and 32 is controlled to reciprocate piston 14 within thechamber 12 at a constant speed. The movement of the permanent magnets24- and 26 through the magnetic flux caused by the coil 43 cuts throughthis flux and generates an alternating current which corresponds infrequency to the frequency of the reciprocating movement of the piston14. The resulting alternating current is fed through lines 52 and 54' tothe point at which the current is needed.

In order to substantially eliminate vertical oscillations of thecylinder caused by the reciprocating movement of the piston, thecylinder 10 may be provided with cross members 74 and 76. Cross members74 and 76 are mounted within weighted springs 78 and 80, respectively,which are supported by thesupport members 82 and 84, respectively. Thesprings 78 and 30 are tuned dynamic vibration absorbers designed toreduce or eliminate the vertical oscillations of the cylinder.

When it is desired to overhaul this invention, it is only necessary thatthe bolts 53 be removed, the cylinder head 56 removed, and the piston 14taken out of the chamber 12. After the overhauling operations, thepiston is simply inserted in the chamber 1 2 and the head 56 replacedand the generator of electric current is ready for reuse.

I claim:

1. A generator of electric current comprising: a cylinder; inducedcurrent coils mounted in recesses formed in the inside perimeter of saidcylinder; a free piston of uniform diameter throughout its length andhaving permanent magnetic material adapted to reciprocate within thecylinder whereby induced currents are generated by the displacement ofthe piston; a pair of inlets in said cylinder for the introduction intosaid cylinder of an explosive fluid mixture, said inlets beinglocated-so that fluid mixture exploded in the cylinder impinges uponeach end of the piston; and a pair of exhausts in said cylinder.

2. A generator of electric current comprising: a cylinder; inducedcurrent coils mounted in recesses formed in the inside perimeter of saidcylinder; a free piston of uniform diameter throughout its lengthiandhaving a transverse portion of permanent magnetic material adapted toreciprocate within the cylinder whereby induced currents are generatedby the displacement of the piston; a pair of inlets in said cylinder forthe introduction into said cylinder of an explosive fluid mixture, saidinlets being located so that fluid mixture exploded in the cylinderimpinges upon each end of the piston; and a pair of exhausts in saidcylinder.

3. A generator of electric current comprising: a cylinder having annularrecesses formed in the inside Wall thereof, said recesses extendingoutwardly from the chamber of the cylinder; induced current coilsmounted in said recesses; an annular insulating insert of heat resistantmaterial inserted in the entrance of each recess to protect the inducedcurrent coils from the heat in the chamberyand a free piston of uniformdiameter through- 1 out its length and having permanent magneticmaterial adapted to reciprocate within the cylinder whereby inducedcurrents are generated by the displacement of the piston; a pair ofinlets in said cylinder for the introduction into said cylinder of anexplosive fluid mixture, said inlets being located so that fluid mixtureexploded in the cylinder impinges upon each end of the piston; and apair of exhausts in said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Publication, Linear Rate Generator, by Stauder, A.I.E.E.,Conference Paper No. 58-79, May 7, 1958.

1. A GENERATOR OF ELECTRIC CURRENT COMPRISING: A CYLINDER; INDUCEDCURRENT COILS MOUNTED IN RECESSES FORMED IN THE INSIDE PERIMETER OF SAIDCYLINDER; A FREE PISTON OF UNIFORM DIAMETER THROUGHOUT ITS LENGTH ANDHAVING PERMANENT MAGNETIC MATERIAL ADAPTED TO RECIPROCATE WITHIN THECYLINDER WHEREBY INDUCED CURRENTS ARE GENERATED BY THE DISPLACEMENT OFTHE PISTON; A PAIR OF INLETS IN SAID CYLINDER FOR THE INTRODUCTION INTOSAID CYLINDER OF AN EXPLOSIVE FLUID MIXTURE, SAID INLETS BEING LOCATEDSO THAT FLUID MIXTURE EXPLODED IN THE CYLINDER IMPINGES UPON EACH END OFTHE PISTON; AND A PAIR OF EXHAUSTS IN SAID CYLINDER.